The present disclosure relates to paper feed devices, document transport devices, and image forming apparatuses which detect with a sensor whether a sheet of paper has been set, and perform retry processing of repeating, a prescribed number of times, intermittent paper feed in which a paper feed operation is performed again when paper feed has failed.
In an image forming apparatus such as a multifunctional peripheral, a copier, a printer, or a facsimile machine, a document or other sheet of paper is set (placed) on a prescribed position, and a feeding rotary body is rotated to feed the paper. When the rotary body is worn or paper is slippery, the paper may not be fed appropriately even if the feeding rotary body is rotated. Thus, some image forming apparatuses have the function of performing retry processing in which the feeding rotary body is once stopped and then rotated again.
For example, as a typical sheet feeder, the following sheet feeder is known. A sheet loaded and fed is detected on the way of the sheet transport path. When a predetermined time has elapsed from the start of feeding a sheet without the sheet being detected, the paper feed is retried. The number of times of such retries can be arbitrarily set, and the paper feed can be retried up to the set number of times. With this configuration, the number of times of paper feed retries is set arbitrarily in accordance with the friction factor of the sheet fed or the wear state of the feeding roller, and the occurrence of paper jam is determined after the paper feed is retried the set number of times, in an attempt to suppress unnecessary jam processing.